Cardioprotective effect exerted by Timosaponin BⅡ through the regulation of endoplasmic stress-induced apoptosis

•TBⅡ effectively improved cardiac function in rats with acute myocardial infarction.•TBⅡ blocked the signaling pathways of ER stress and their associated apoptosis proteins expression.•TBⅡ inhibited the apoptosis of cardiomyocytes via the PI3K/AKT pathway. Timosaponin BⅡ (TBⅡ), one of the primary bioactive compounds from Anemarrhena asphodeloides Bunge, possesses potential cardioprotective effects. However, the mechanism underlying TBⅡ-mediated cardioprotection, especially the involvement of endoplasmic reticulum stress, remains largely unknown. This study was designed to evaluate the role of TBⅡ in myocardial injury protection and explore its possible mechanisms. In vivo models of isoproterenol-induced myocardial injury and H2O2-induced cytotoxicty were established to investigate the effect of anti-myocardial injury of TBⅡ. The potential mechanisms were investigated in vitro and in vivo using multiple detection methods like electrocardiography, histo-pathological examination, JC-1 staining, TUNEL staining, ELISA technology, and western blot analysis. In vivo study revealed that TBⅡ improved electrocardiography and heart vacuolation, reduced myocyte apoptosis, and improved the antioxidant potential. In vitro investigation demonstrated that TBⅡ pretreatment inhibited ER stress-mediated apoptosis pathways. Further investigation of the underlying mechanisms revealed that TBⅡ prevented H2O2-induced H9c2 cardiomyocytes injury by the PI3K/Akt pathways, whereas the addition of LY294002, the pharmacologic antagonist of PI3K, attenuated TBⅡ-induced expression of apoptotic protein and cytoprotective effects. These results suggested that TBⅡ protects against myocardial injury in vitro and enhances cellular defense capacity by inhibiting ER stress-mediated apoptosis pathways in vivo by activating the PI3K/Akt pathways. [Display omitted]